This invention relates to improvements in fish egg incubation systems.
After fish eggs have been gathered from the mother fish and fertilized, they must be carefully handled in order to obtain a high-survival rate of fish from the initial eggs. During the formation stages, the eggs need to be in a protective environment where they will not be eaten by adult fish or damaged by rough movement and will have sufficient oxygen and moisture to support their continued life. When one egg dies, a fungus is often formed on it which, if permitted to spread to other eggs, will block the passage of necessary gases to the surface of the eggs and they, too, will die.
Many systems have been developed for providing a desired environmental for fish eggs during their early stages of formation. In the U.S. patent to Martinez No. 3,464,387, there is provided a fish breeder having a chamber wherein the mother fish is permitted to give birth and a second chamber into which the baby fish can swim through a partition separating the two chambers. The separation partition has adjustable positions to permit in one position the baby fish to enter into the safe chamber to avoid the danger of being eaten by the mother fish. With an adjustment in the partition to a second position, the baby fish is prevented from reentering the first chamber.
The U.S. patent to Stasio No. 3,693,591, discloses a fish breeder system which floats within a fish aquarium. This system includes a device which provides a nesting tray below a frame and a series of small chambers located above it with small apertures communicating between the region of the nesting tray and the small chambers. The newborn fish escape from the nesting tray and the adult fish by entering into the upper chambers through the small apertures which are designed to provide easy access into the chamber but difficult exit of the small fish back out of the safe chambers.
The fish breeder shown in the Freudenberger U.S. Pat. No. 3,374,770 is formed from a large molded plastic box having perforated walls which permit the flow of water into the chamber from the aquarium and provide a safe cage for the small fish until they are of a large enough size to be released from the breeder.
More elaborate spawning trays and fish egg incubators have been developed for providing suitable environments for the formation of eggs into alevins. In the U.S. patent to Brittain et al No. 3,024,764, there is disclosed a fish tray system which includes a screen egg holder cartridge for holding up to 8,000 individual eggs. The egg holding cartridge is placed within a tray and the trays are stacked to permit the flow of water from one tray to the screen and then on to the next lower tray. The cartridge provides a means for holding the eggs during incubation stage and in subsequent fry culture stages. The entire cartridge can be detached from the incubation hatchery tray to float in a rearing pond while protecting the fry from predatory attack. There is no disclosure, however, that the individual eggs are separated from one another during the incubation stage.
A somewhat similar tray system is described in the U.S. patent to Tuttle No. 3,028,837 which includes a mesh screen upon which are distributed a plurality of eggs to be hatched. In a similar manner, the U.S. patent to Reynolds No. 3,738,317 utilizes a screened holder having a chamber for holding the eggs between two screens during the incubation of the eggs. This screen may be a fine mesh fabric or semi-rigid fiberglass material which will provide little obstruction to water flow.
One solution for the fungus problem is that set forth in the Reynolds U.S. Pat. No. 3,738,317 wherein the water utilized in the system is subjected to ultraviolet rays to kill inhibiting fungus.
It is known in the poultry industry to provide stackable trays for holding incubating eggs with each tray having individual egg supporting chambers and thin members extending up from the tray to prevent the falling of the egg in one aperture against the egg in an adjacent aperture as the trays are moved from a horizontal to inclined position. Such a tray system is shown in the U.S. patent to Theilig No. 3,147,737.
Perhaps the most pertinent prior system is disclosed in the U.S. patent to Salter No. 4,014,293. As shown, a fish egg incubator includes an upper screen tray for supporting the eggs. When the eggs hatch out, the alevins fall through the mesh in the screen to a rugose substrate where the alevins reside as they continue their development to the fry stage. The egg supporting screen and the rugose layer are provided within a tray system in which circulated water provides the protective atmosphere for the growth processes to be successful. This system is somewhat complicated, however, by having numerous individual parts which must be carefully manufactured in view of the necessary clearances.
None of the above-mentioned patents, however, disclose the provision of a quiet environment to permit fish eggs to rest during the formation of the alevin without contacting one another to prevent the spread of fungus and to provide a nearly stationary position for the alevin during its conversion from yoke to fish tissue without wasting nutrition on movement.
Among the objects of the present invention are to provide a simple system for supporting fertilized fish eggs during their development to viable fry; to minimize the loss due to spreading fungus; and to minimize the loss of conversion of yoke to body tissue due to unnecessary activity of the alevins.
It is another object of this invention to provide a supporting system for developing fish eggs which can be used in rearing ponds from the very outset without the need for a separate hatchery facility and without the need for changing the location of the egg from the time it is first placed into the system for incubation to the time that the alevins have matured into viable fry.